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Chemical coordination looks like a short chapter, but it is dense. Almost every line in it pairs a gland with a hormone, a hormone with an action, or an action with a disorder, and exam questions are built by mixing those pairs up. This post gives you a map of the chapter, explains the one mechanism you need, works through a typical matching question and ends with a routine for revising it.
What does the NEET syllabus include from this chapter?
The NEET (UG) 2026 syllabus notified by the National Medical Commission lists, under human physiology: endocrine glands and hormones; the hypothalamus, pituitary, pineal, thyroid, parathyroid, adrenal, pancreas and gonads; the mechanism of hormone action (elementary idea); the role of hormones as messengers and regulators; and hypo- and hyperactivity disorders, naming dwarfism, acromegaly, cretinism, goitre, exophthalmic goitre, diabetes and Addison's disease. It adds that diseases are "to be dealt in brief". In NCERT this is Class 11 Chapter 19, Chemical Coordination and Integration.
Biology carries 90 of the 180 questions in the NEET (UG) 2026 information bulletin, so a chapter like this is worth a few sure marks. Check the bulletin for your own exam year, since NTA publishes a new one each time.
What counts as a hormone?
NCERT gives the current definition: hormones are "non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts". Endocrine glands have no ducts, so their secretions go into the blood. The definition also covers tissues that are not glands: the atrial wall of the heart makes atrial natriuretic factor (ANF), which lowers blood pressure; the kidney makes erythropoietin, which stimulates red blood cell formation; and the gut makes gastrin, secretin, cholecystokinin and gastric inhibitory peptide.
Which gland makes which hormone?
Hypothalamus: releasing and inhibiting hormones that control the anterior pituitary (for example GnRH, and somatostatin, which inhibits growth hormone release). It also makes oxytocin and vasopressin, which travel down axons to the posterior pituitary.
Pituitary: the pars distalis makes growth hormone, prolactin, TSH, ACTH, LH and FSH; the pars intermedia makes MSH; the neurohypophysis releases oxytocin and vasopressin (ADH).
Pineal: melatonin, which regulates the 24-hour rhythm of sleep and body temperature.
Thyroid: thyroxine (T₄) and triiodothyronine (T₃), which regulate basal metabolic rate, and thyrocalcitonin (TCT), which regulates blood calcium.
Parathyroid: parathyroid hormone (PTH), which raises blood Ca²⁺.
Thymus: thymosins, which drive the differentiation of T-lymphocytes.
Adrenal medulla: adrenaline and noradrenaline, the "fight or flight" catecholamines.
Adrenal cortex: glucocorticoids (mainly cortisol) and mineralocorticoids (mainly aldosterone, which increases Na⁺ and water reabsorption).
Pancreas: α-cells make glucagon, which raises blood glucose; β-cells make insulin, which lowers it.
Testis: Leydig cells make androgens, mainly testosterone.
Ovary: growing follicles make estrogen; the corpus luteum makes mainly progesterone.
Which disorders does the syllabus name?
Too little growth hormone in childhood gives pituitary dwarfism; too much gives gigantism; too much in adults gives acromegaly.
Impaired ADH release gives diabetes insipidus: the kidney cannot conserve water.
Iodine deficiency causes hypothyroidism and goitre; hypothyroidism during pregnancy can cause cretinism in the baby.
Exophthalmic goitre (Graves' disease) is a form of hyperthyroidism, with protruding eyeballs and weight loss.
Underproduction by the adrenal cortex causes Addison's disease.
Insulin deficiency or resistance causes diabetes mellitus.
Insulin's story is a good reminder that this chapter is real medicine: Frederick Banting and John Macleod shared the 1923 Nobel Prize in Physiology or Medicine "for the discovery of insulin".
How do hormones act on target cells?
Hormones bind specific receptors, and NCERT sorts them by where the receptor sits. Hormones that bind membrane-bound receptors usually do not enter the cell; they generate second messengers such as cyclic AMP, IP₃ and Ca²⁺. Hormones that bind intracellular receptors, mainly steroids and iodothyronines (thyroid hormones), act on the genome and regulate gene expression. NCERT's four chemical classes are peptide or protein hormones (insulin, glucagon), steroids (cortisol, testosterone, estradiol, progesterone), iodothyronines, and amino-acid derivatives (epinephrine).
Worked example: a matching question
Which pair is correctly matched? (a) PTH: hypocalcemic (b) Glucagon: hypoglycemic (c) Aldosterone: Na⁺ reabsorption in renal tubules (d) ADH: made in the posterior pituitary.
PTH increases blood calcium, so it is hypercalcemic. (a) is wrong.
Glucagon raises blood glucose, so it is hyperglycemic. (b) is wrong.
Aldosterone acts on renal tubules to increase Na⁺ and water reabsorption. (c) is right.
ADH is made by the hypothalamus and only released from the posterior pituitary. (d) is wrong.
Answer: (c). Notice that each wrong option flips one word: "hypo" for "hyper", "made" for "released". That is the pattern to watch for.
Common mistakes and how to avoid them
Mixing up diabetes insipidus and mellitus. Insipidus is about ADH and water; mellitus is about insulin and glucose.
Confusing TCT and PTH. Both act on calcium. PTH raises blood calcium; NCERT pairs TCT with it as the other regulator.
Forgetting non-gland hormones. ANF, erythropoietin and the four gut hormones are easy marks.
A revision routine for this chapter
On a blank page, write each gland and, beside it, every hormone, action and disorder you can recall. Then check against NCERT in a different colour.
Two days later, do it again without looking. Roediger and Karpicke (2006) found that students who practised recalling a passage remembered more of it two days and a week later than students who reread it, even though rereading made them more confident.
Make cards for the pairs you got wrong. Our guide to flashcards that work shows how to write them.
Revise this chapter alongside neural control and coordination, since questions often contrast the two systems.
If one idea will not stick, such as why steroid hormones act on genes, the Fermi Concept Library has every concept in biology with its own lesson, so you can fix that gap and return to your chapter.
Tonight, draw the gland-hormone-action-disorder chain from memory for the thyroid, adrenal and pancreas, then check it against NCERT.
